For the mounting of semiconductor chips, so-called die bonders are used as automatic assembly machines with which a bondhead picks up the semiconductor chip to be mounted at a first location and places it on a substrate at a second location. The bondhead has a pick-up tool with a vacuum nozzle with which the semiconductor chip is held during transport. Different measuring systems have been developed for checking whether the semiconductor chip has been successfully picked. With a first measuring system, a photosensor is located in the bondhead at the upper end of the vacuum nozzle. On the way from the first location to the substrate the pick-up tool passes over a light source which then produces a light-induced pulse in the photosensor when no semiconductor chip is located on the pick-up tool. Because of space reasons, an optimum development of the measuring system is not possible as the bondhead must fulfil various functions with the lowest possible mass.
With another known measuring system, the semiconductor chip is led through a light barrier during transport. The disadvantage with this system is that the light barrier must be adjusted exactly at the transport height.
Measurement of the strength of the vacuum in the vacuum nozzle which should be greater when the semiconductor chip has been picked and the nozzle sealed has only partially proved to be suitable because the sealing by means of the semiconductor chip is often very poor with die collet pick-up tools.
The object of the invention is to develop a measuring system which reliably detects whether a semiconductor chip is located on the pick-up tool and which does not have to be adjusted.